Xenon short arc lamps



March 1961 w. E. THOURET XENON SHORT ARC LAMPS 2 Sheets-Sheet 1 Filed Jan. 28, 1958 INVENTOR. 14/04 F6A/V6 f. 72/00/857 BY OV B March 7, 1961 Filed Jan. 28, 1958 W. E. THOURET XENON SHORT ARC LAMPS 2 Sheets-Sheet 2 1N VEN TOR. WOLF6/7A 6 f. 59 00/957 XENON SHORT ARC LAMPS Filed Jan. 28, 1958, Ser. No. 711,669

11 Claims. (Cl. 313-113) This invention is concerned with xenon short are light sources.

The general object of the invention is to provide a novel form of lamp of this type having an approximately rectangular arc brightness distribution.

Other and more detailed objects of the invention will be apparent from the following description of the embodiment thereof selected for disclosure purposes.

The selected embodiment is illustrated in the attached drawings, in which Figure 1 is a view partly in elevation and partly in cross section with some parts broken away of a xenon short are lamp embodying the structural features of this invention;

Figure 2 is a similar view taken at right angles to the view of Fig. 1;

Figures 3 and 4 are diagrammatic illustrations of the actual arc distribution and of the apparent arc distribution respectively;

Figure 5 is a diagrammatic illustration of the lamp circuit; and

Figure 6 is a diagrammatic illustration of the reflector lamp combination illustrating one assembly form suitable for general application.

As is well known in this art, xenon short are lamps consist generally of an anode and a cathode sealed in a quartz envelope containing a relatively high pressure xenon atmosphere of between 3 to 18 atmospheres. The anode and cathode are separated by a relatively short distance and produce an intense are having a very useful continuous spectrum extending substantially through the visible infra-red and ultraviolet ranges.

In the usual form of lamp of this type a single anode and a single cathode are axially aligned and properly spaced and between which the arc is formed. As is well known this are is generally of conical form with the apex lying at the cathode. This arc brightness distribution is not suitable for some uses and the general purpose of this invention is to provide a lamp structure which generates an arc in which the arc brightness distribution is more rectangular, that is approximating a square in elevation as distinguished from the single cathode form of lamp in which it appears triangular in elevation The manner in 'which this is accomplished will be most readily understood by direct reference to the lamp illustrated in the accompanying drawings As shown therein the lamp includes an evacuated envelope 10 which for structural strength is preferably of spherical form and is constructed of quartz for well understood reasons. The envelope 10 is provided with axially aligned stems, as shown at 12 and 14. Mounted in the stem 12 is an anode of refractory metal, usually swaged tungsten. As illustrated it consists of a rod-like States Patent, 0

portion 16 mounted in the stem and terminating at the Patented Mar. 7, 1961 bons 20 which are sealed inthe stem and provide current lead connections. The number of ribbons required and their geometrical arrangement depends upon the lamp wattage, as is well known in the art. These ribbons are all electrically connected to a metallic connector 22 to which a flexible properly insulated heavy current lead 24 is mechanically and electrically attached. The end of the stem 12 is provided with a two-fold insulating housing or base 26 and the parts are secured together by means of a metal clamp 28.

The stem 14 and construction of the related parts is generally similar, differing however in accordance with this invention in that at least two cathodes, three or more can be used, 30 and32 are mounted thereon. These cathodes are axially aligned with the anode 16 and 18 and are symmetrically positioned on opposite side of the axis of the envelope which includes the axis of the anode. The cathodes are preferably positioned and are of such a size so that they lie entirely within the projection of the cross-section of the area of the anode 18 (see Figures 1, 3 and 4). Stated another way, the diameter of the complete cathode structure is less than the diameter of the anode structure. The cathodes 30 and 32 are individually supplied with current through the refractory ribbon leads 34 and 36 which are sealed in the stem 14. Connection terminals 38 and 40 are individually provided for the cathodes and they in turn are provided with connection fixtures 42 and 44, see Figs 1 and 2. The stem 14 is likewise enclosed at the end by means of a two part housing or base 46, the parts of which are held in place by means of a metal clamp 48.

Mounted on the anode 18 or supported within the envelope 10 in anyother suitable manner is a sphericalor parabolical reflector 52, preferably made of molybdenum. As illustrated, the reflector 52 is secured to theanode by means of a fixture 50 of any suitable form which interconnects them in any suitable manner. The reflector 52, is preferably mounted so that its focal point falls at the center of the are which is generated between the cathodes and the anode. 1

This type of lamp is direct current operated and there is illustrated in Fig. 5 a suitable energizing circuit for the lamp. One side of the source is connected to the anode 18 and the other side is connected to the cathodes 30 and 32. This latter connection includes any suitable form of current limiting ballast 54 such as would be commonly used with a lamp of this type.

In a single arc type of xenon short are lamp, that is one employing a single anode and a single cathode, the arc brightness distribution is of conical form'and lies on the axis of the aligned electrodes. The arc brightness distribution or that is the arc itselflwould have the form of the arcs A and B of Fig. 3. However, when a pair of cathodes are used in accordance with this invention, two arcs, that is the arcs A and B are formed and they partially overlap so that in combination they form a generally rectangular pattern, as illustrated.

However, the arc brightness distribution is still further improved and made to approach a rectangular pattern by the use of the internal spherical or parabolical reflector 52 illustrated'by Fig, 4. The inverted image of the arcs A and B of Fig. 3 is reflected into the arcs themselves as shown in Fig. 4, where the anode 18 and the cathodes 30 and 32 form part of the total reflection and they also appear inverted, as shown at 18', 30"and 32 respectively. It follows, therefore, that the light distribution pattern produced by the lamps'containing'the'double arc plus the internal reflector is substantially rectangular in form and relatively uniform throughout its area, providing a lighting pattern which is highly useful for many purposes including searchlights, projection apparatus and other optical devices.

It will be understood that the example illustrated in Fig. 6 is but one example of the possible use and advantages of the subject matter of this invention. The particular arrangement of Pig. 6 provides a combination suitable for use in a Searchlight or other-equivalent device.

From the above description it will be apparent to those skilled in the art that some variation in details of this invention will be apparent. It is preferable, therefore, that the scope of protection afforded hereby be determined by the appended claims rather than by the illustrative embodiment herein detailed.

What is claimed is:

1. A lighting combination comprising in combination a parabolic reflector, a xenon short are lamp at the focal point of said reflector having at least two cathodes aligned with an anode, and a spherical reflector facing said parabolic reflector positioned with its focal point at the focal point of said spherical reflector, the focal length of said spherical reflector being shorter than the focal length of said parabolic reflector.

2. A lighting combination comprising in combination a parabolic reflector, a xenon short are lamp at the focal point of said reflector having a pair of cathodes aligned with an anode, and a spherical reflector supported within said envelope with its focal point coincident with the focal point of said parabolic reflector the focal length of said spherical reflector being less than the focal length of said parabolic reflector.

3. A short are lamp for producing a substantially rectangular arc brightness distribution comprising a sealed envelope having an axis thereacross, an anode of a predetermined size and shape having a major axis, means for mounting said anode within said envelope with the major axis of the anode lying along the axis of said envelope, said anode having a cross-sectional area of a predetermined size and shape lying in a plane perpendicular to said envelope axis, a plurality of cathode electrodes of predetermined size and shape, means for mounting said cathode electrodes within said envelope with the major axis of each cathode electrode lying substantially parallel to said envelope axis, said cathode electrodes being mounted with a gap between the anode and each of said cathode electrodes in which an anode-cathode arc is produced, the cross-sectional areas of said cathodes in a plane perpendicular to said envelope axis being within an area on said last named plane which is of the same size and shape as the said cross-sectional area of said anode.

4. A short are lamp for producing a substantially rectangular arc brightness distribution comprising a sealed envelope having an axis thereacross, an anode of a predetermined size and shape having a major axis, means for mounting said anode within said envelope with the major axis of the anode lying along the axis of said envelope, said anode having a cross-sectional area of a predetermined size and shape lying in a plane perpendicular to said envelope axis, a plurality of cathode electrodes of predetermined size and shape, means for mounting said cathode electrodes within said envelope with the major axis of each cathode electrode lying substantially parallel to said envelope axis, said cathode-electrodes being mounted with a gap between the anode and each of said cathode electrodes in which an anode-cathode arc is produced, the cross-sectional areas of said cathodes in a plane perpendicular to said envelope axis being within an area on said last named plane which is of the same size and shape as the said cross-sectional area of said anode, a reflector, and means for supporting said reflector within said envelope so that its focal point lies at the center of the are produced in the gap between the anode and the cathode electrodes.

5. A short are lamp as set forth in claim 3 wherein said envelope is sealed and contains a xenon atmosphere.

6. A xenon short are lamp for producing a substantially rectangular high brightness arc comprising a sealed quartz envelope which is filled with xenon gas under high pressure, an anode electrode mounted within said envelope, and a plurality of cathode electrodes mounted opposite one end of said anode electrode with a gap therebetween.

7. A xenon short are lamp for producing a substantially rectangular arc brightness distribution comprising a sealed envelope containing a xenon atmosphere, an anode electrode mounted with an active end within said envelope, a plurality of cathode electrodes mounted within said envelope opposite said active end of said anode and leaving a gap therebetween, the shape of the electrodes and the spacing therebetween being such as to establish a conical arc in the gap between each cathode electrode and said anode.

8. A short are lamp as set forth in claim 4 wherein said envelope is sealed and contains a xenon atmosphere.

9. A short are lamp as set forth in claim 3 wherein the said cross-sectional area of each of said cathodes is smaller than the said cross-section of said anode.

10. A short are lamp for producing a substantially rectangular arc brightnes distribution comprising a sealed envelope, a substantially cylindrical anode electrode having a conically tapering surface at one end thereof mounted within said envelope, a cathode structure including at least two cathode electrodes, each of said cathode electrodes being substantially cylindrical and having a conically tapering end and being of a diameter smaller than the diameter of said anode, and means for mounting the cathode electrodes of said structure with their conical ends opposite the conical end of said anode with a gap therebetween thereby producing a substantially conical arc in the gap between each cathode electrode and said anode.

11. A short are lamp producing a substantially rectangular arc brightness distribution comprising a sealed envelope, a substantially cylindrical anode electrode having a conically tapering surface at one end thereof mounted with saidenvelope, a cathode structure including at least two cathode electrodes, each of said cathode electrodes being substantially cylindrical and having a conically tapering end and being of a diameter smaller than the diameter of said anode, means for mounting the cathode electrodes of said structure with their conical ends opposite the conical end of said anode with a gap therebetween thereby producing a substantially conical arc in the gap between each cathode electrode and said anode, a reflector, means for mounting said reflector wtihin said envelope so that its focal point lies at substantially the center of the arc in the gap between the cathodes and said anode.

References Cited in the file of this patent 

